FIELD OF THE INVENTION
The invention relates to a sand-dispensing device for motor vehicles, having at least one refillable sand container, from which a sand channel leads to the area in front of one of the vehicle's wheels, and there forms a sand outlet, having a flap that closes the outlet from below, and which has a heating system in the area of the outlet.
Sanding systems are already known for railroad rolling stock and for motor vehicles and serve to increase traction between the wheel and the track, or the roadway, respectively. It is also known that heating systems can be used in order to prevent the sand from freezing in the colder seasons of the year.
A sanding system described in German unexamined patent application No. 1 530 025 is intended for railroad vehicles that are powered by internal combustion engines. In this regard, the exhaust gases from the internal combustion engine are so routed that they flow around the outlet pipe of the sanding system. The sanding systems described in U.S. Pat. No. 1,204,665 and in U.S. Pat. No. 1,292,353 are also intended for railroad vehicles; in these systems a portion of the sand channel is heated, in one case electrically and in the other by steam a portion of the sand channel that is to be heated is wound around with a heating wire; here, however, the sand channel is configured as a double-walled pipe. However, sanding systems used on railroad vehicles can only be compared to a limited extent to motor vehicles, since they are exclusively stationary systems that are always available, even in the warmer times of the year, primarily for emergency braking. Furthermore, most of them are operated by compressed air, which is usually available in railroad vehicles. In contrast to this, sanding systems for motor vehicles are intended for use in the colder periods of the year and their sanding channels and outlets are exposed to road spray, as when the vehicle passes through puddles and the like. For this reason, motor vehicle sanding systems are seldom needed, and when they are used, unfavorable conditions exist that can affect operational safety and traffic safety. Since, in the case of motor vehicles, it is not enough to heat a small portion of the sand channel near the outlet, even through compressed air may be used, because the ingress of road spray can cause icing of the sand channel in any portion throughout its entire length, it has been proposed in Austrian patent AT No. 353,621 that the whole length of the sand channel, including the outlet area, be heated.
From U.S. Pat. No. 2,182,969 and Austrian Pat. No. 198,146 it is also known that the exhaust gases from the engine can be routed to the sand container or the outlet, respectively, in order to provide for heating the sand. In this connection, the inner bottom is movable, so that it can be moved by the pressure of the exhaust gases that pulse in time with the exhaust strokes of the engine. However, such sanding systems do not have individual sanding channels that deliver sand directly ahead of the vehicle wheel, but rather scatter the sand by opening a flap in the container outlet through the oscillating container bottom.
In order to provide the necessary protection against road spray, the arrangement and configuration of flaps, slides and the like at the end of a sanding channel in motor vehicles is also known (see German unexamined patent application No. 2 400 378, U.S. Pat. No. 1,818,815 and Austrian Pat. No. 176,454 and No. 349,328). The arrangement or configuration of flaps naturally provides good protection for the sand channel and the sand outlet against road spray, although this simply displaces the problem of icing from the sand channel to the closing flap whose trouble-free operation must be ensured at any time.